Use AJV, refactor a lot

api/models/validation.js

@@ -0,0 +1,16 @@
+const Ajv = require(`ajv`);
+
+const { validationError } = require(`../utils`);
+
+const validateOrThrow = (schema, data) => {
+	const ajv = new Ajv();
+	const valid = ajv.validate(schema, data);
+
+	if (!valid) {
+		throw validationError(ajv.errors);
+	}
+};
+
+module.exports = {
+	validateOrThrow,
+};